Do not pass tile grid to getTile and tileUrlFunc

getTile and the tileUrlFunc are functions of the source, so they do need to be passed the tile grid. The tile source knows its tile grid, and can get the projection's tile grid if it doesn't have a tile grid.
Don't recompute delay every loop
Don't schedule a new post render delay if one is already active
Merge pull request #451 from fredj/dev

Don't recompute delay every loop
Store kinetic coordinates and time as numbers instead of objects
Merge pull request #453 from fredj/dev

Store kinetic coordinates and time as numbers instead of objects
Merge pull request #452 from twpayne/limit-post-renderer-set-timeout

Don't schedule a new post render delay if one is already active
Download Plovr into build directory

This means that all build artefacts except for the examples are in
build.
Add logging messages to indicate when a download is in progress
Add logging messages for downloading proj4js
Merge pull request #454 from twpayne/download-plovr-into-build-dir

Download plovr into build dir
Merge pull request #450 from elemoine/projection-null

Do not pass tile grid to getTile and tileUrlFunc
Map view options may be a literal object
Examples do not create ol.View2D instances